Single Turbo vs Twin Turbos

[bradleyland]

Originally Posted by flinchy

also, due to how gearing works, acceleration at redline relative to in a higher gear should pretty much always be better.. unless your car REALLY tapers off badly.

You'd be amazed how many cars benefit from shifting before redline. This is especially true for turbo charged cars where the torque band comes on early. I've done plots on a couple of cars (one turbo, one NA), and both benefited from shifting before redline. The turbo charged one more so than the NA. Both were running stock ECU software.

Gearing multiplies torque, but it does not affect power. Peak acceleration will come at peak power. Engines like the S54 will work best when shifted at redline, but that's the exception, not the rule (for road cars).

[ozinaldo]

Originally Posted by bradleyland

You'd be amazed how many cars benefit from shifting before redline. This is especially true for turbo charged cars where the torque band comes on early. I've done plots on a couple of cars (one turbo, one NA), and both benefited from shifting before redline. The turbo charged one more so than the NA. Both were running stock ECU software.

Gearing multiplies torque, but it does not affect power. Peak acceleration will come at peak power. Engines like the S54 will work best when shifted at redline, but that's the exception, not the rule (for road cars).

+1. Just to add my impressions with the N54 version in the 1M; better overall acceleration if you shift around 5500 to 6000 (depending on outside/road condition) for 1st to second gear and at 6500-6700 range for 2-3-4. Couldn't find an opportunity to pass 6500 at 5th or 6th yet

And to clarify, 1M goes to redline with little to no complaint, there is still good power and torque at 6000s but there are no real gains to stay after 6000 too long and I found that shifting like stated above puts you back at the exact sweet spot again to continue acceleration. Other notes for whoever unfamiliar are redline is at 7000, fuel cut comes a bit after which should be avoided. My Mustang dyno runs on the stock car showed that torque reaches its peak around 2600 rpm and stays almost constant till 6000, very little fall till 6500. HP reached its peak around 5300-5500 rpm and after that smoothly falls till 6500, nothing like a sharp fall which supports butt dyno impressions.

[flinchy]

Originally Posted by bradleyland

You'd be amazed how many cars benefit from shifting before redline. This is especially true for turbo charged cars where the torque band comes on early. I've done plots on a couple of cars (one turbo, one NA), and both benefited from shifting before redline. The turbo charged one more so than the NA. Both were running stock ECU software.

Gearing multiplies torque, but it does not affect power. Peak acceleration will come at peak power. Engines like the S54 will work best when shifted at redline, but that's the exception, not the rule (for road cars).

yeah i know it's beneficial on MANY cars,

gearing still effects acceleration, if you have a 14:1 overall ratio and xxx HP, it'll accelerate faster than 13:1 and xxx+10 HP, until your HP drops way down closer to redline

even if power drops of WAY before redline, it's always beneficial to go a LITTLE past peak power, to the point a higher gear will accelerate you faster.

turbo cars SHOULD make peak power at redline, with anappropriate sized turbo etc.. as any power production should be overcome by pushing in more air.. cars like the N54, howeer, weren't designed from te start as racecar style, so the turbos can't push that far.


graphs of RB turbos show that peak power CAN be made at or near 7000rpm in the N54.. peak torque almost holds to there as well (but a huge hump a bit below 6)

[Bimmer13]

Originally Posted by bradleyland

In what way would it help? What is the benefit of knowing your boost level in a stock car? Once you're modded, I totally understand, but stock, I just don't see the benefit.

Peak boost is not necessarily peak power (horsepower). Peak boost will often correspond with peak force (ft-lbs/newton-meters), but if you're driving for performance, you're more interested in power band and power peak.

If you're interested in knowing where your engine performs best, go do a dyno run. They're usually pretty cheap. If you're running stock, you can just Google image search for 135i N55 dyno and browse the results to get a feeling for where your car is making power.

If you're drag racing, you're most interested in determining shift points. Those are based on acceleration profiles for each gear. Peak acceleration should occur with peak power, so once you have a dyno, you know your shift point (or roughly). With a turbo car, you can sometimes benefit from short shifting a bit. If you really want to know, you get an accelerometer app for your smartphone, and you datalog an acceleration run in each gear. You combine the plots, and you look for the cross-overs. That's your shift point.

Well it would help at the very least in simply knowing that the turbo is at full boost. Just like the red line on your RPM gauge.

[shah269]

Why do you need a boost gauge?
Simple to remind you when you can smile and laugh like a lunatic to and from work.
That's why BMW!
A car is a car is a car is a car! of 1k cars you sell only 50 ever see a real track. The other 99% don't!
So make me smile you subdued German fucks!

[ChristianReyess]

Originally Posted by flinchy

a boost gague is more useful for diagnosing issues, if you're not hodling boost smoothly, or not hitting targets, you can clearly see it on a gauge...

also, due to how gearing works, acceleration at redline relative to in a higher gear should pretty much always be better.. unless your car REALLY tapers off badly.

all you have to look out for is don't hit the limiter, as the car retards and loses LOTS of power and acceleration.

our cars shouldn't be driven to redline, we lose retarded amounts of power towards the end of our RPM range. Or atleast that is how I feel with my baby.


And a JB4 would get you your PSI levers and it is very sensitive and accurate. As mentioned before.

[Adam135]

Originally Posted by ChristianReyess

our cars shouldn't be driven to redline, we loose retarded amounts of power towards the end of our RPM range.

Yeah, I don't normally go past about 5500rpm.

[shah269]

pppffffttt! no wonder this car is crap in the snow....1500rpm and it can spin its tires!
I mentor some great kids for FIRST Robotics comps and one of the kids asked me why my car didn't come stock with dual turbo gauges.
Well me being the "adult" said something about costs and bla bla bla
and one of the kids says with out even blinking an eye....
"Turbo gauges for tubro cars are like fake tits....sure they don't do much but they are sure pretty to look at!"
And with that I was done for the day!

[ozinaldo]

Originally Posted by shah269

pppffffttt! no wonder this car is crap in the snow....1500rpm and it can spin its tires!
I mentor some great kids for FIRST Robotics comps and one of the kids asked me why my car didn't come stock with dual turbo gauges.
Well me being the "adult" said something about costs and bla bla bla
and one of the kids says with out even blinking an eye....
"Turbo gauges for tubro cars are like fake tits....sure they don't do much but they are sure pretty to look at!"
And with that I was done for the day!

Don't know how many years old was that kid was but for sure he is a clever one regardless. I don't mind not having fake tits inside my car though

[flinchy]

Originally Posted by ChristianReyess

our cars shouldn't be driven to redline, we lose retarded amounts of power towards the end of our RPM range. Or atleast that is how I feel with my baby.


And a JB4 would get you your PSI levers and it is very sensitive and accurate. As mentioned before.

erh, just check out the graph just posted, you'll see it's only a moderate drop from 5,500rpm peak... 310-290 at 6500rpm, you could work it out based on gear ratios the optimum shift point, it'll be somewhere between 6500-7000... i'll work it out tomorrow sometime, i'm too tired for math

JB4 doesn't get you a SUPER accurate gauge, only your temp gauge hijacked.

Originally Posted by Adam135

Yeah, I don't normally go past about 5500rpm.

lol why? just losing acceleration

the second benefit of shifting higher, is if you shift at say 6250rpm, the higher gear will be waaay off he low side of the power band, probably even down below 250hp in that graph

shift at 6500-7000, even as low as 280hp, and you'll 'drop down' into a much higher 270-280 range.. and 280hp in 2nd gear has more acceleration than 280hp in third, so either way, staying in the higher gear until AT LEAST 6500rpm gives you better acceleration...

acceleration isn't about peak power, it's about average power, how much area there is below you on the graph... i could work it out better if the dyno operator actually stuck it to above 6500, it may very well be worth going much closer to 7000.

[Adam135]

Originally Posted by flinchy

lol why? just losing acceleration

the second benefit of shifting higher, is if you shift at say 6250rpm, the higher gear will be waaay off he low side of the power band, probably even down below 250hp in that graph

shift at 6500-7000, even as low as 280hp, and you'll 'drop down' into a much higher 270-280 range.. and 280hp in 2nd gear has more acceleration than 280hp in third, so either way, staying in the higher gear until AT LEAST 6500rpm gives you better acceleration...

acceleration isn't about peak power, it's about average power, how much area there is below you on the graph... i could work it out better if the dyno operator actually stuck it to above 6500, it may very well be worth going much closer to 7000.

Thanks, that makes sense.

[flinchy]

Originally Posted by Adam135

Thanks, that makes sense.

no worries

don't get me wrong, once you get way past 5500, past 6500 it'll feel WAY slower, just like you all say

doesn't mean it's slower acceleration than shifting up though.

[ChristianReyess]

Originally Posted by flinchy

erh, just check out the graph just posted, you'll see it's only a moderate drop from 5,500rpm peak... 310-290 at 6500rpm, you could work it out based on gear ratios the optimum shift point, it'll be somewhere between 6500-7000... i'll work it out tomorrow sometime, i'm too tired for math

JB4 doesn't get you a SUPER accurate gauge, only your temp gauge hijacked.



lol why? just losing acceleration

the second benefit of shifting higher, is if you shift at say 6250rpm, the higher gear will be waaay off he low side of the power band, probably even down below 250hp in that graph

shift at 6500-7000, even as low as 280hp, and you'll 'drop down' into a much higher 270-280 range.. and 280hp in 2nd gear has more acceleration than 280hp in third, so either way, staying in the higher gear until AT LEAST 6500rpm gives you better acceleration...

acceleration isn't about peak power, it's about average power, how much area there is below you on the graph... i could work it out better if the dyno operator actually stuck it to above 6500, it may very well be worth going much closer to 7000.

Didn't really think about where you would drop to at the higher gear. That makes a lot of sence!

[Angerman]

Originally Posted by Bimmer13

why it doesn't have a gauge?

Buy one if you want it....

http://www.**********s.com/P3-Cars-V...MW-135i-1M.htm